The shifting has come as a bit of a surprise with three weeks left until voters head to the polls to decide the Nov. 21 runoff between the two. The latest prognostications picked up national headlines, as Louisiana is one of just three states with gubernatorial elections this year.

Most forecasters had initially predicted an easy win for the GOP, particularly after Democrat Mary Landrieu’s crushing defeat in last year’s U.S. Senate race.

A conservative Southern state, Louisiana has no Democratic statewide elected officials, and Edwards, who chairs the state House Democratic Caucus, was not a well-known political player in the run-up to the election, while Vitter has won two statewide elections to the U.S. Senate.

Both Edwards and Vitter have spent this week hitting the campaign trail and shoring up coveted endorsements.

Edwards won the Louisiana Sheriffs’ Association’s backing. Vitter’s been adding to his list of Republican leaders who are backing his run, including the Louisiana Oil and Gas Association and state legislators.

Their campaigns and groups supporting them quickly took to the television airwaves with mostly negative political ads.

The outcome was widely seen as a blow to Vitter, who for months had bested or only slightly trailed Edwards in the polls.

Kyle Kondik, an analyst for Sabato’s Crystal Ball, out of the University of Virginia’s Center for Politics, writes that Vitter maintains a “slight edge” in the runoff, but the forecaster will be monitoring the race to determine whether it shifts more to the Democratic side to be a clear “toss-up.”

“Louisiana has transitioned to a Republican state, but Vitter will test the political gravity of the Pelican State in next month’s gubernatorial runoff,” writes Nathan L. Gonzales, of the Rothenberg & Gonzales Political Report. “There are plenty of unanswered questions, including how much money the Republican Governors Association is willing to keep sinking into the race and if the Democratic Governors Association sees enough of an opportunity to spend money on television ads.”

And Jennifer Duffy, of the Cook Political Report, writes that Edwards has several challenges — particularly the D behind his name and the well-funded Vitter movement.

“There are plenty of observers of Louisiana politics who have a hard time believing that a Democrat has a real shot at winning the runoff. ... The skepticism is understandable, but the reality remains that this has become a much more competitive race than anyone would have predicted six months ago,” she adds.

Polls in the days leading up to Saturday’s primary and in the days since have shown Edwards with a slight edge over Vitter in the runoff match-up.

Still, the forecasters note that Edwards needs at least 25 percent of the Republican vote if he hopes to win.

The three combined Republicans on Saturday’s ballot made up 57 percent of the vote.

“In order to win, Edwards would need to capture roughly a quarter of the votes cast for the other two Republican candidates,” Kondik writes.

Jared Leopold, spokesman for the Democratic Governors Association, said the latest shift is a direct indictment of Vitter as the GOP’s candidate.

“The polls in this race make it clear: Louisiana voters don’t trust David Vitter to be their governor,” he said.

The RGA, however, says it’s confident in its candidate.

“The RGA will help ensure voters know who the real Edwards is: a tax-raising Obama liberal who would wreck Louisiana. David Vitter is the only candidate in this race who offers the conservative leadership that will move the state forward,” RGA spokesman Jon Thompson said.